Determinants and Impact of Giardia Infection in the First 2 Years of Life in the MAL-ED Birth Cohort

Comparative performance evaluation of four different methods for diagnosing Giardia infection in dogs and zoonotic assemblages' identification

Giardia duodenalis (syn. G. intestinalis or G. lamblia) is a parasitic protozoan that infects the upper intestinal tract of a broad range of hosts, including humans and domestic animals. Thus, it has raised concerns about the public health risk due to companion animals. Recently, with the improvement of living standards and increasing contacts between pets and humans, the zoonotic transmission of Giardia has dramatically increased. From a genetic point of view, G. duodenalis should be viewed as a complex species that includes eight different species-specific genetic assemblages. The laboratory diagnosis is mainly based on the finding of microscopic cysts in stool samples by coprological examination. Other methods include the detection of antigens, immunoassays or PCR protocols, which allow the identification of Giardia assemblages. The study aimed to compare the performance of Direct Fluorescence Antibody test (DFA), zinc sulfate flotation technique (ZnSO4), rapid diagnostic test (RDT), end-point PCR amplification (PCR) for the detection of Giardia and to identify the concerning assemblages in a canine population from Central Italy. Direct fluorescence antibody test is the reference standard for laboratory diagnosis of Giardia in fecal samples from dogs, despite the microscopic examination after flotation remains the most useful method in many veterinary diagnostic centers. The present findings demonstrate the high performance of DFA and ZnSO4 in detecting Giardia, while RDT may be useful as alternative or complementary method to the DFA and ZnSO4. PCR performance was low, but it allowed determining Giardia B zoonotic assemblage in 25% of the PCR-positive specimens (15 out of 60), while the remaining PCR-positive isolates belonged to the dog-specific assemblage C. The 26% prevalence of G. duodenalis detected by DFA in owned dogs and the identification of potentially zoonotic assemblages underline the potential risk for public health and indicate frequent cross-species transmission of the parasite between humans and dogs.

Examining the molecular epidemiology of Giardia and Eimeria species in Japan: a comprehensive review

Globally, animals and humans suffer from diarrheal illnesses due to protozoan parasites such as Giardia and Eimeria species. The molecular epidemiology of these parasites in Japan is summarized in this review. In humans, researchers found only one main species of Giardia, which is most referred to as G. lamblia, but it's also known by different names like G. duodenalis or G. intestinalis. However, within this species, six assemblages (A, B, C, D, E, and F) were found in animals, and assemblage B was frequently recorded in human and monkey populations, whereas assemblages A and E were predominant in calves. Assemblage A was found in sika deer and assemblages A, C, D, and F were predominant in dogs, cats, and ferret. Eimeria bovis, E. zuernii, and other species found in animals made up the group of species known as Eimeria spp., with E. bovis and E. zuernii being the most common in cattle. Our review highlighted a notable lack of data investigations regarding these two pathogens in water and environmental sources. Giardia cysts were found in the few studies that have been done on water sources, suggesting that water may play a significant role in the transmission of Giardia species. Our review suggests that further research is necessary to fully comprehend the molecular diversity and dynamics of transmission of Giardia spp. and Eimeria spp. in humans, animals, and environmental sources in Japan.

Associations between Shared Sanitation, Stunting and Diarrhoea in Low-Income, High Density Urban Neighbourhoods of Maputo, Mozambique - a Cross-Sectional Study

INTRODUCTION

Shared sanitation facilities are used by over 500 million people around the world. Most research evidence indicates that shared sanitation conveys higher risk than household sanitation for many adverse health outcomes. However, studies often fail to account for variation between different types of shared facilities. As informal housing development outpaces sanitation infrastructure, it is imperative to understand which components of shared facilities may mitigate the health risks of shared sanitation use.

METHODS

This cross-sectional study determines whether sanitation improvement or compound hygiene were associated with stunting or diarrhoeal prevalence in children under five living in Maputo, Mozambique who rely on shared sanitation facilities. The study uses logistic and linear multivariable regression analysis to search for associations and control for potential confounding factors.

RESULTS

346 children (43.9%) in the study population were stunted. Each unit increase in sanitation score was associated with an approximate decrease of 22% in the odds of stunting (OR: 0.78, CI: 0.66, 0.92), and an increase in height of 0.23 height-for-age z-scores (CI: 0.10, 0.36). There was no evidence that the compound hygiene score was associated with height as measured by stunting (OR: 1.05, CI: 0.87, 1.26) or z-score (-0.06, CI: -0.21, 0.09). Neither sanitation nor compound hygiene score were associated with diarrhoea in the population.

CONCLUSIONS

Use of an improved shared latrine is associated with decreased odds of stunting. There is no evidence of an association between latrine improvement and diarrhoea. Further investigation is necessary to isolate attributes of shared sanitation facilities that may reduce health risks.

Giardia intestinalis reshapes mucosal immunity toward a Type 2 response that attenuates inflammatory bowel-like diseases

Diarrheal diseases are the second leading cause of death in children worldwide. Epidemiological studies show that co-infection with Giardia intestinalis decreases the severity of diarrhea. Here, we show that Giardia is highly prevalent in the stools of asymptomatic school-aged children. It orchestrates a Th2 mucosal immune response, characterized by increased antigen-specific Th2 cells, IL-25, Type 2-associated cytokines, and goblet cell hyperplasia. Giardia infection expanded IL-10-producing Th2 and GATA3+ Treg cells that promoted chronic carriage, parasite transmission, and conferred protection against Toxoplasma gondii-induced lethal ileitis and DSS-driven colitis by downregulating proinflammatory cytokines, decreasing Th1/Th17 cell frequency, and preventing collateral tissue damage. Protection was dependent on STAT6 signaling, as Giardia-infected STAT6-/- mice no longer regulated intestinal bystander inflammation. Our findings demonstrate that Giardia infection reshapes mucosal immunity toward a Type 2 response, which confers a mutualistic protection against inflammatory disease processes and identifies a critical role for protists in regulating mucosal defenses.

Giardia lamblia Diagnosed During Upper Gastrointestinal Endoscopy: Clinical Manifestation, Histopathologic Findings and the Association With Celiac Disease

BACKGROUND

Giardia lamblia may be found incidentally during upper gastrointestinal (GI) endoscopy, including when biopsies are taken for celiac disease (CeD) diagnosis. We aimed to study the clinical presentation and histopathology of G. lamblia and determine its association with CeD.

METHODS

A retrospective case series of pediatric patients diagnosed with G. lamblia based on intestinal biopsies between January 1999 and January 2023. Baseline data; demographics, symptoms, celiac serology, stool testing, macroscopic and histopathologic findings. Follow-up data; treatment and repeated celiac serology.

RESULTS

Of 38 patients with G. lamblia , 15 (39.5%) were female, mean age of 6.7 (±4.8 SD) years. Clinical symptoms; GI 19/38 (50%), growth retardation and/or iron deficiency anemia 8/38 (21.1%) or a combination 11/38 (28.9%). Celiac serology was positive in 13/38 (34.2%). Duodenal endoscopic findings; normal (n = 23, 60.5%), nodularity (n = 12, 32.4%), erosions in 2 (5.4%) and scalloping in 1 (2.7%). Histopathology; normal villi 24/38 (63.2%), villous shortening with increased intraepithelial lymphocytes (IEL) 5/38 (13.2%), isolated IEL 3/38 (7.9%) and duodenitis in 6/38 (15.8%). Children with positive CeD serology were younger (4 vs. 8.1 years, P = 0.019), had fewer GI symptoms (23.1% vs. 64%, P = 0.017) and a higher rate of villous shortening with increased IEL (38.5% vs. 0, P < 0.001) versus children with negative serology. On follow-up, metronidazole treatment was recommended to all but was documented to be given in 22/38 (57.9%). Among the 13 children with positive CeD serology, serology normalized in 10 (77%).

CONCLUSIONS

G. lamblia is a rare histopathologic finding in children. It may be an incidental finding in CeD or may cause false positive celiac serology.

Current Understanding of Giardia lamblia and Pathogenesis of Stunting and Cognitive Deficits in Children from Low- and Middle-Income Countries

Purpose of Review

Giardia lamblia is a common intestinal parasite worldwide, mainly in children from low- and middle-income countries (LMIC). Also, it has been associated with increased intestinal permeability, stunting, and cognitive impairment. Nonetheless, the pathogenesis of long-term consequences is difficult to elucidate.

Recent Findings

Recent studies try to understand the long-term consequences of Giardia infections. First, well-characterized studies associate Giardia with intestinal damage and child growth. Second, infections appear not to be associated with inflammation, but "lack of inflammation" may not, however, entirely exclude a pro-inflammatory pathway. Finally, some important amino acids are lower and could contribute to prolongate stunting and cognitive deficit.

Summary

Giardia infections in LMIC used to be associated with child growth shortfalls, gut permeability, and cognitive deficits. Multifactorial effects could be associated with Giardia, including nutritional, altered microbiota, and generation of potentially toxic microbial metabolic byproducts, all together increasing risk of long-term outcomes.

Prevalence and assemblage of Giardia duodenalis in a case-control study of children under 5 years from Jimma, Southwest Ethiopia

Giardia duodenalis is a common pathogenic intestinal protozoan parasite with high prevalence in developing countries, especially among children. The distribution of giardia assemblages among humans and their clinical relevance remains controversial. This study aimed to determine the prevalence and assemblage of Giardia among children under 5 years of age in Jimma, Southwest Ethiopia. Employing a case-control design, 606 children presenting with diarrhea at Jimma university medical center and Serbo Health Center were enrolled from December 2016 to July 2018 along with 617 matched controls without diarrhea. Giardia was detected and typed using real-time PCR. Univariate and multivariate regression analysis was performed. The total prevalence of Giardia was 41% (501/1223) and did not differ significantly between cases and controls (40% vs 42%). Prevalence increased by age, with the highest prevalence seen in children aged ≥ 25 months. Children without diarrhea with a history of diarrhea during the last month were more likely to be Giardia positive compared to children with no history diarrhea (OR 1.8 and 95%CI; 1.1-2.9). Regardless of current diarrhea symptoms, assemblage B predominated with 89%, followed by assemblage A (8%) and mixed infection assemblage A and B (3%). We report a high prevalence of Giardia by PCR detection in Jimma, Ethiopia, with assemblage B being predominant. There was a similar distribution of Giardia assemblages between children with and without diarrhea. Increasing age was a risk factor for Giardia infection. Community-based prevention and control strategies need to be employed to decrease the risk of giardia infection.

A diagnostic stewardship approach to prevent unnecessary testing of an enteric bacterial molecular panel

IMPORTANCE

Testing for enteric bacterial pathogens in patients hospitalized for more than 3 days is almost always inappropriate. Our study validates the utility of the 3-day rule and the use of clinical decision support tools to decrease unnecessary testing of enteropathogenic bacteria other than C. difficile. Overriding the restriction was very low yield. Our study highlights the importance of diagnostic stewardship and further refines the criteria for allowing providers to override the restriction while monitoring the impact of the interventions.

Improved household flooring is associated with lower odds of enteric and parasitic infections in low- and middle-income countries: A systematic review and meta-analysis

Enteric and parasitic infections such as soil-transmitted helminths cause considerable mortality and morbidity in low- and middle-income settings. Earthen household floors are common in many of these settings and could serve as a reservoir for enteric and parasitic pathogens, which can easily be transmitted to new hosts through direct or indirect contact. We conducted a systematic review and meta-analysis to establish whether and to what extent improved household floors decrease the odds of enteric and parasitic infections among occupants compared with occupants living in households with unimproved floors. Following the PRISMA guidelines, we comprehensively searched four electronic databases for studies in low- and middle-income settings measuring household flooring as an exposure and self-reported diarrhoea or any type of enteric or intestinal-parasitic infection as an outcome. Metadata from eligible studies were extracted and transposed on to a study database before being imported into the R software platform for analysis. Study quality was assessed using an adapted version of the Newcastle-Ottawa Quality Assessment Scale. In total 110 studies were eligible for inclusion in the systematic review, of which 65 were eligible for inclusion in the meta-analysis after applying study quality cut-offs. Random-effects meta-analysis suggested that households with improved floors had 0.75 times (95CI: 0.67-0.83) the odds of infection with any type of enteric or parasitic infection compared with household with unimproved floors. Improved floors gave a pooled protective OR of 0.68 (95CI: 0.58-0.8) for helminthic infections and 0.82 OR (95CI: 0.75-0.9) for bacterial or protozoan infections. Overall study quality was poor and there is an urgent need for high-quality experimental studies investigating this relationship. Nevertheless, this study indicates that household flooring may meaningfully contribute towards a substantial portion of the burden of disease for enteric and parasitic infections in low- and middle-income settings.

Epidemiology of giardiasis and assemblages A and B and effects on diarrhea and growth trajectories during the first 8 years of life: Analysis of a birth cohort in a rural district in tropical Ecuador

BACKGROUND

There are limited longitudinal data on the acquisition of Giardia lamblia infections in childhood using molecular assays to detect and type assemblages, and measure effects of infections on diarrhea risk and childhood growth.

METHODS

We analysed stool samples from a surveillance sample within a birth cohort in a rural district in tropical Ecuador. The cohort was followed to 8 years of age for the presence of G. lamblia in stools by quantitative PCR and A and B assemblages by Taqman assay or Sanger sequencing. We explored risk factors associated with infection using generalized estimating equations applied to longitudinal binary outcomes, and longitudinal panel data analysis to estimate effects of infection on diarrhea and growth trajectories.

RESULTS

2,812 stool samples collected between 1 month and 8 years of age from 498 children were analyzed and showed high rates of infection: 79.7% were infected at least once with peak prevalence (53.9%) at 5 years. Assemblage B was accounted for 56.8% of genotyped infections. Risk factors for infection included male sex (P = 0.001), daycare attendance (P<0.001), having a household latrine (P = 0.04), childhood (P<0.001) and maternal soil-transmitted helminth (P = 0.029) infections, and exposures to donkeys (age interaction P = 0.034). G. lamblia was associated with increased risk of diarrhea (per episode, RR 1.03, 95% CI 1.01-1.06, P = 0.011) during the first 3 years of life and a transient impairment of weight (age interaction P = 0.017) and height-for-age (age interaction P = 0.025) trajectories between 1 and 4 years of age. There was no increased risk of either assemblage being associated with outcomes.

CONCLUSION

Our data show a relatively high edemicity of G. lamblia transmission during childhood in coastal Ecuador, and evidence that infection is associated with a transiently increased risk of diarrhea during the first 3 years of life and impairment of weight and height between 1 and 4 years.

Symptomatic and asymptomatic enteric protozoan parasitic infection and their association with subsequent growth parameters in under five children in South Asia and sub-Saharan Africa

BACKGROUND

Entamoeba histolytica, Giardia, and Cryptosporidium are common intestinal protozoan parasites that contribute to a high burden of childhood morbidity and mortality. Our study quantified the association between intestinal protozoan parasites and child anthropometric outcomes among children under-5.

METHODS

We analyzed data from 7,800 children enrolled in the Global Enteric Multicenter Study (GEMS) across seven study sites that were positive for intestinal protozoan parasites between December 2007 and March 2011. Parasites were assessed using stool immunoassays (ELISA). We applied multiple linear regression to test the association between any or concurrent parasite and child anthropometric outcomes: length/height-for-age (HAZ), weight-for-age (WAZ), and weight-for-length/height (WHZ) z-score after 60 days of enrollment. Models were stratified by diarrheal symptoms, driven by the study design, and adjusted for potential covariates.

FINDINGS

During the follow-up at day 60 after enrollment, child anthropometric outcomes, among the asymptomatic children showed, negative associations between Giardia with HAZ [β: -0.13; 95% CI: -0.17, -0.09; p<0.001] and WAZ [β -0.07; 95% CI: -0.11, -0.04; p<0.001], but not WHZ [β: -0.02; 95% CI:-0.06, 0.02; p = 0.36]; Cryptosporidium with WAZ [β: -0.15; 95% CI: -0.22, -0.09; p<0.001] and WHZ [β: -0.18; 95%CI: -0.25, -0.12; p<0.001], but not with HAZ [β: -0.03; 95% CI: -0.09, 0.04; p = 0.40]. For symptomatic children, no associations were found between Giardia and anthropometry; negative associations were found between Cryptosporidium with HAZ [β: -0.17; 95% CI: -0.23, -0.11; p<0.001], WAZ [β: -0.25; 95% CI: -0.31, -0.19; p<0.001] and WHZ [β: -0.23; 95% CI: -0.30, -0.17; p<0.001]. Among the asymptomatic 24-59 months children, Giardia had a negative association with HAZ [β: -0.09; 95% CI: -0.15, -0.04; p = 0.001]. No significant associations were found between E. histolytica with child growth.

CONCLUSIONS

While some studies have found that Giardia is not associated with (or protective against) acute diarrhea, our findings suggest that it is associated with growth shortfall. This observation underscores the need for preventive strategies targeting enteric protozoan parasites among young children, to reduce the burden of childhood malnutrition.

The Gut-Wrenching Effects of Cryptosporidiosis and Giardiasis in Children

Cryptosporidium species and Giardia duodenalis are infectious intestinal protozoan pathogens that cause alarming rates of morbidity and mortality worldwide. Children are more likely to have clinical symptoms due to their less developed immune systems and factors such as undernutrition, especially in low- and middle-income countries. The severity of the symptoms and clinical manifestations in children may vary from asymptomatic to life-threatening depending on the Cryptosporidium species/G. duodenalis strains and the resulting complex stepwise interactions between the parasite, the host nutritional and immunologic status, and the gut microbiome profile. Structural damages inflicted by both parasites to epithelial cells in the large and small intestines could severely impair children's gut health, including the ability to absorb nutrients, resulting in stunted growth, diminished neurocognitive development, and other long-term effects. Clinically approved cryptosporidiosis and giardiasis drugs have broad antimicrobial effects that have incomprehensible impacts on growing children's gut health.

Long-term impacts of an urban sanitation intervention on enteric pathogens in children in Maputo city, Mozambique: study protocol for a cross-sectional follow-up to the Maputo Sanitation (MapSan) trial 5 years postintervention

INTRODUCTION

We previously assessed the effect of an onsite sanitation intervention in informal neighbourhoods of urban Maputo, Mozambique on enteric pathogen detection in children after 2 years of follow-up (Maputo Sanitation (MapSan) trial, ClinicalTrials.gov: NCT02362932). We found significant reductions in Shigella and Trichuris prevalence but only among children born after the intervention was delivered. In this study, we assess the health impacts of the sanitation intervention after 5 years among children born into study households postintervention.

METHODS AND ANALYSIS

We are conducting a cross-sectional household study of enteric pathogen detection in child stool and the environment at compounds (household clusters sharing sanitation and outdoor living space) that received the pour-flush toilet and septic tank intervention at least 5 years prior or meet the original criteria for trial control sites. We are enrolling at least 400 children (ages 29 days to 60 months) in each treatment arm. Our primary outcome is the prevalence of 22 bacterial, protozoan, and soil transmitted helminth enteric pathogens in child stool using the pooled prevalence ratio across the outcome set to assess the overall intervention effect. Secondary outcomes include the individual pathogen detection prevalence and gene copy density of 27 enteric pathogens (including viruses); mean height-for-age, weight-for-age, and weight-for-height z-scores; prevalence of stunting, underweight, and wasting; and the 7-day period prevalence of caregiver-reported diarrhoea. All analyses are adjusted for prespecified covariates and examined for effect measure modification by age. Environmental samples from study households and the public domain are assessed for pathogens and faecal indicators to explore environmental exposures and monitor disease transmission.

ETHICS AND DISSEMINATION

Study protocols have been reviewed and approved by human subjects review boards at the Ministry of Health, Republic of Mozambique and the University of North Carolina at Chapel Hill. Deidentified study data will be deposited at https://osf.io/e7pvk/.

TRIAL REGISTRATION NUMBER

ISRCTN86084138.

Giardia hinders growth by disrupting nutrient metabolism independent of inflammatory enteropathy

Giardia lamblia (Giardia) is among the most common intestinal pathogens in children in low- and middle-income countries (LMICs). Although Giardia associates with early-life linear growth restriction, mechanistic explanations for Giardia-associated growth impairments remain elusive. Unlike other intestinal pathogens associated with constrained linear growth that cause intestinal or systemic inflammation or both, Giardia seldom associates with chronic inflammation in these children. Here we leverage the MAL-ED longitudinal birth cohort and a model of Giardia mono-association in gnotobiotic and immunodeficient mice to propose an alternative pathogenesis of this parasite. In children, Giardia results in linear growth deficits and gut permeability that are dose-dependent and independent of intestinal markers of inflammation. The estimates of these findings vary between children in different MAL-ED sites. In a representative site, where Giardia associates with growth restriction, infected children demonstrate broad amino acid deficiencies, and overproduction of specific phenolic acids, byproducts of intestinal bacterial amino acid metabolism. Gnotobiotic mice require specific nutritional and environmental conditions to recapitulate these findings, and immunodeficient mice confirm a pathway independent of chronic T/B cell inflammation. Taken together, we propose a new paradigm that Giardia-mediated growth faltering is contingent upon a convergence of this intestinal protozoa with nutritional and intestinal bacterial factors.

Trophozoite fitness dictates the intestinal epithelial cell response to Giardia intestinalis infection

Giardia intestinalis is a non-invasive, protozoan parasite infecting the upper small intestine of most mammals. Symptomatic infections cause the diarrhoeal disease giardiasis in humans and animals, but at least half of the infections are asymptomatic. However, the molecular underpinnings of these different outcomes of the infection are still poorly defined. Here, we studied the early transcriptional response to G. intestinalis trophozoites, the disease-causing life-cycle stage, in human enteroid-derived, 2-dimensional intestinal epithelial cell (IEC) monolayers. Trophozoites preconditioned in media that maximise parasite fitness triggered only neglectable inflammatory transcription in the IECs during the first hours of co-incubation. By sharp contrast, "non-fit" or lysed trophozoites induced a vigorous IEC transcriptional response, including high up-regulation of many inflammatory cytokines and chemokines. Furthermore, "fit" trophozoites could even suppress the stimulatory effect of lysed trophozoites in mixed infections, suggesting active G. intestinalis suppression of the IEC response. By dual-species RNA-sequencing, we defined the IEC and G. intestinalis gene expression programs associated with these differential outcomes of the infection. Taken together, our results inform on how G. intestinalis infection can lead to such highly variable effects on the host, and pinpoints trophozoite fitness as a key determinant of the IEC response to this common parasite.

Effects of High Temperature and Heavy Precipitation on Drinking Water Quality and Child Hand Contamination Levels in Rural Kenya

Climate change may impact human health through the influence of weather on environmental transmission of diarrhea. Previous studies have found that high temperatures and heavy precipitation are associated with increased diarrhea prevalence, but the underlying causal mechanisms have not been tested and validated. We linked measurements of Escherichia coli in source water (n = 1673), stored drinking water (n = 9692), and hand rinses from children <2 years old (n = 2634) with publicly available gridded temperature and precipitation data (at ≤0.2 degree spatial resolution and daily temporal resolution) by the GPS coordinates and date of sample collection. Measurements were collected over a 3-year period across a 2500 km² area in rural Kenya. In drinking water sources, high 7-day temperature was associated with a 0.16 increase in log₁₀ E. coli levels (p < 0.001, 95% CI: 0.07, 0.24), while heavy 7-day total precipitation was associated with a 0.29 increase in log₁₀ E. coli levels (p < 0.001, 95% CI: 0.13, 0.44). In household stored drinking water, heavy 7-day precipitation was associated with a 0.079 increase in log₁₀ E. coli levels (p = 0.042, 95% CI: 0.07, 0.24). Heavy precipitation did not increase E. coli levels among respondents who treated their water, suggesting that water treatment can mitigate effects on water quality. On child hands, high 7-day temperature was associated with a 0.39 decrease in log₁₀ E. coli levels (p < 0.001, 95% CI: -0.52, -0.27). Our findings provide insight on how climate change could impact environmental transmission of bacterial pathogens in Kenya. We suggest water treatment is especially important after heavy precipitation (particularly when preceded by dry periods) and high temperatures.

Antigen-Based Diagnosis of Human Giardiasis: A Systematic Review and Meta-Analysis

Background

We aimed to present a systematic review and meta-analysis of studies that used antigen-based assays for the diagnosis of human giardiasis.

Methods

All the related published literature cited within PubMed, ISI web of science, Google Scholar, Embase, and Scopus, were searched up to December 2021. The search terms, both as MeSH terms and text words, were "Giardia", "Giardia lamblia", "Giardia intestinalis", "giardiasis", combined with "diagnosis", "antigen detection", serodiagnosis, or serological diagnosis. The required data was extracted from the papers. Pooled estimates of sensitivity and specificity were obtained and forest plots and summary receiver operating characteristics (SROC) plots were used to calculate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results

The search of databases found 1683 papers, of which 46 articles fulfilled our eligibility criteria. The sensitivity of antigen-based methods for the diagnosis of human giardiasis ranged from 45% (95% CI: 31-59%) to 100% (95% CI: 100-100%) and the pooled estimate of sensitivity was 92% (95% CI: 90-93%). The pooled estimated specificity was 97% (95% CI: 96-98%), ranged from 81% (95% CI: 68-89%) to 100% (95% CI: 98-100%). The summary estimate of PPV and NPV were 92 % (95% CI: 90-93%) and 97% (95% CI: 96-98%) respectively. Comparing the performance of the antigen detection assays by region revealed a significant difference in the assay's performances in different regions of the world.

Conclusion

The antigen-based detection methods have acceptable and satisfactory performance in the diagnosis of human giardiasis. The task ahead is to identify more specific target antigens and design simpler, cheaper, and more sensitive methods for the diagnosis of this common worldwide-distributed parasitic infection.

Impact of enteropathogens on faltering growth in a resource-limited setting

Introduction

Environmental enteropathy is an important contributor to childhood malnutrition in the developing world. Chronic exposure to fecal pathogens leads to alteration in intestinal structure and function, resulting in impaired gut immune function, malabsorption, and growth faltering leading to environmental enteropathy.

Methods

A community-based intervention study was carried out on children till 24 months of age in Matiari district, Pakistan. Blood and fecal specimens were collected from the enrolled children aged 3-6 and 9 months. A real-time PCR-based TaqMan array card (TAC) was used to detect enteropathogens.

Results

Giardia, Campylobacter spp., enteroaggregative Escherichia coli (EAEC), Enteropathogenic Escherichia coli (EPEC), Enterotoxigenic Escherichia coli (ETEC), and Cryptosporidium spp. were the most prevailing enteropathogens in terms of overall positivity at both time points. Detection of protozoa at enrollment and 9 months was negatively correlated with rate of change in height-for-age Z (ΔHAZ) scores during the first and second years of life. A positive association was found between Giardia, fecal lipocalin (LCN), and alpha 1-Acid Glycoprotein (AGP), while Campylobacter spp. showed positive associations with neopterin (NEO) and myeloperoxidase (MPO).

Conclusion

Protozoal colonization is associated with a decline in linear growth velocity during the first 2 years of life in children living in Environmental enteric dysfunction (EED) endemic settings. Mechanistic studies exploring the role of cumulative microbial colonization, their adaptations to undernutrition, and their influence on gut homeostasis are required to understand symptomatic enteropathogen-induced growth faltering.

Infections and nutrient deficiencies during infancy predict impaired growth at 5 years: Findings from the MAL-ED study in Pakistan

Background

Socio-economic, nutritional, and infectious factors have been associated with impaired infant growth, but how the presence of these factors during infancy affects growth around 5 years is not well understood.

Methods

This secondary analysis of the MAL-ED cohort included 277 children from Pakistan for whom socio-demographic, breastfeeding, complementary foods, illness, nutritional biomarkers, stool pathogens and environmental enteropathy indicators between 0 and 11 months were recorded. We used linear regression models to analyze associations of these indicators with height-for-age (HAZ), weight-for-age (WAZ) and weight-for-height (WLZ) at 54-66 months (~5 years), and Poisson regression with robust standard errors to estimate risk ratios for stunting and underweight ~5 years, controlling for gender, first available weight, and income.

Results

Among the 237 infants followed longitudinally and evaluated at about 5 years of age, exclusive breastfeeding was short (median = 14 days). Complementary feeding started before 6 months with rice, bread, noodles, or sugary foods. Roots, dairy products, fruits/vegetables, and animal-source foods were provided later than recommended (9-12 months). Anemia (70.9%), deficiencies in iron (22.0%), zinc (80.0%), vitamin A (53.4%) and iodine (13.3%) were common. Most infants (>90%) presented with diarrhea and respiratory infections in their first year. At ~5 years, low WAZ (mean-1.91 ± 0.06) and LAZ (-2.11 ± 0.06) resulted in high prevalence of stunting (55.5%) and underweight (44.4%) but a relatively low rate of wasting (5.5%). While 3.4% had concurrent stunting and wasting ~5 years, 37.8% of children had coexisting stunting and underweight. A higher income and receiving formula or dairy products during infancy were associated with a higher LAZ ~5 years, but infant's history of hospitalizations and more respiratory infections were associated with lower LAZ and higher risk of stunting ~5 years. Infants' intake of commercial baby foods and higher serum-transferrin receptors were associated with higher WAZ and lower risk of underweight ~5 years. Presence of Campylobacter and fecal neopterin >6.8 nmol/L in the first year were associated with increased risk of underweight ~5 years.

Conclusion

Growth indicators ~5 years were associated with poverty, inappropriate complementary feeding, and infections during the first year of life, which supports the early start of public health interventions for preventing growth delay ~5 years.

Derivation and external validation of clinical prediction rules identifying children at risk of linear growth faltering

Background

Nearly 150 million children under-5 years of age were stunted in 2020. We aimed to develop a clinical prediction rule (CPR) to identify children likely to experience additional stunting following acute diarrhea, to enable targeted approaches to prevent this irreversible outcome.

Methods

We used clinical and demographic data from the Global Enteric Multicenter Study (GEMS) to build predictive models of linear growth faltering (decrease of ≥0.5 or ≥1.0 in height-for-age z-score [HAZ] at 60-day follow-up) in children ≤59 months presenting with moderate-to-severe diarrhea, and community controls, in Africa and Asia. We screened variables using random forests, and assessed predictive performance with random forest regression and logistic regression using fivefold cross-validation. We used the Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) study to (1) re-derive, and (2) externally validate our GEMS-derived CPR.

Results

Of 7639 children in GEMS, 1744 (22.8%) experienced severe growth faltering (≥0.5 decrease in HAZ). In MAL-ED, we analyzed 5683 diarrhea episodes from 1322 children, of which 961 (16.9%) episodes experienced severe growth faltering. Top predictors of growth faltering in GEMS were: age, HAZ at enrollment, respiratory rate, temperature, and number of people living in the household. The maximum area under the curve (AUC) was 0.75 (95% confidence interval [CI]: 0.75, 0.75) with 20 predictors, while 2 predictors yielded an AUC of 0.71 (95% CI: 0.71, 0.72). Results were similar in the MAL-ED re-derivation. A 2-variable CPR derived from children 0-23 months in GEMS had an AUC = 0.63 (95% CI: 0.62, 0.65), and AUC = 0.68 (95% CI: 0.63, 0.74) when externally validated in MAL-ED.

Conclusions

Our findings indicate that use of prediction rules could help identify children at risk of poor outcomes after an episode of diarrheal illness. They may also be generalizable to all children, regardless of diarrhea status.

Funding

This work was supported by the National Institutes of Health under Ruth L. Kirschstein National Research Service Award NIH T32AI055434 and by the National Institute of Allergy and Infectious Diseases (R01AI135114).

The Influence of Selected Factors on the Detection of Giardia intestinalis by Microscopic and Immunoenzymatic Methods

Background

Giardia intestinalis is one of the most common parasites in humans. Contaminated food and water can be a source of infection. Substances added to food are intended to increase its safety. We aimed to determination of the influence of various microorganisms and compounds that stimulate digestive functions, as well as preservatives and antioxidants on the detection of G. intestinalis by microscopic and immunoenzymatic methods.

Methods

Twenty stool samples, archived in 1998-2018 in the Provincial Sanitary and Epidemiological Station in Bydgoszcz (Poland), collected both from patients referred for parasitic examinations by a doctor of a medical facility and from private individuals, were used to assess the impact of selected factors (such as bacterial strains, viruses and substances added to food) on the detection of G. intestinalis by microscopic and immunoenzymatic methods.

Results

G. intestinalis was detected by both microscopic and immunoenzymatic methods with the same sensitivity (100%). The result of the G. intestinalis determination was positive in 90% of the samples after the addition of potassium sorbate, and in 25% of the samples after the addition of citric acid.

Conclusion

The presence of other microorganism such as bacteria and viruses does not influence on the detection of G. intestinalis by microscopic and immunoenzymatic methods in stool samples. Citric acid as an antioxidant added to foods affects the detection of G. intestinalis. Due to the small number of samples used, it is necessary to continue research on the impact of various factors on the detection of protozoa.

Extensive testing of a multi-locus sequence typing scheme for Giardia duodenalis assemblage A confirms its good discriminatory power

BACKGROUND

The flagellated parasite Giardia duodenalis is a major and global cause of diarrhoeal disease. Eight genetically very distinct groups, known as assemblages A to H, have been recognized in the G. duodenalis species complex, two of which (assemblages A and B) infect humans and other mammalian hosts. Informative typing schemes are essential to understand transmission pathways, characterize outbreaks and trace zoonotic transmission. In this study, we evaluated a published multi-locus sequence typing (MLST) scheme for G. duodenalis assemblage A, which is based on six polymorphic markers.

METHODS

We genotyped 60 human-derived and 11 animal-derived G. duodenalis isolates collected in Europe and on other continents based on the published protocol. After retrieving previously published genotyping data and excluding isolates whose sequences showed allelic sequence heterozygosity, we analysed a dataset comprising 146 isolates.

RESULTS

We identified novel variants at five of the six markers and identified 78 distinct MLST types in the overall dataset. Phylogenetic interpretation of typing data confirmed that sub-assemblage AII only comprises human-derived isolates, whereas sub-assemblage AI comprises all animal-derived isolates and a few human-derived isolates, suggesting limited zoonotic transmission. Within sub-assemblage AII, isolates from two outbreaks, which occurred in Sweden and Italy, respectively, had unique and distinct MLST types. Population genetic analysis showed a lack of clustering by geographical origin of the isolates.

CONCLUSION

The MLST scheme evaluated provides sufficient discriminatory power for epidemiological studies of G. duodenalis assemblage A.

Exclusive Breastfeeding and Childhood Morbidity: A Narrative Review

Globally, diarrheal diseases and acute respiratory infections are the leading causes of morbidity and mortality in children under 5 years old. The benefits of exclusive breastfeeding in reducing the risk of gastrointestinal and respiratory infections are well documented. Optimal breastfeeding may potentially save the lives of about 800,000 children in low-income settings. Despite the evidence, around 63% of infants from birth to 6 months are not exclusively breastfed worldwide. We searched the literature published between 2010 and 2022 in Medline, Embase, and Scopus on the association between exclusive breastfeeding and infectious diseases. We selected and reviewed 70 relevant studies. Our findings expand and confirm the positive association between exclusive breastfeeding and reduced risk of a number of gastrointestinal, respiratory, and other infections in 60 out of 70 studies observed in both low- and high-income settings. Several studies analyzing exclusive breastfeeding duration reported that a longer exclusive breastfeeding duration is protective against many infectious diseases. This review also reported a lack of standardized definition for measuring exclusive breastfeeding in many studies. Overall, the results highlight the benefits of exclusive breastfeeding in many studies and suggests reporting exclusive breastfeeding in future studies using a consistent definition to enable better monitoring of exclusive breastfeeding rates.

Giardia and growth impairment in children in high-prevalence settings: consequence or co-incidence?

PURPOSE OF REVIEW

Giardia is a common intestinal parasite worldwide, and infection can be associated with clear, and sometimes persistent symptomatology. However, in children in high-prevalence settings, it is most often not associated with or is perhaps even protective against acute diarrhea. Nonetheless, recent longitudinal studies in high-prevalence settings increasingly identify an association with long-term outcomes that has been difficult to discern.

RECENT FINDINGS

Recent studies have made progress in disentangling this apparent paradox. First, prospective, well characterized cohort studies have repeatedly identified associations between Giardia infection, gut function, and child growth. Second, experimental animal and in-vitro models have further characterized the biological plausibility that Giardia could impair intestinal function and subsequently child development through different pathways, depending upon biological and environmental factors. Finally, new work has shed light on the potential for Giardia conspiring with specific other gut microbes, which may explain discrepant findings in the literature, help guide future higher resolution analyses of this pathogen, and inform new opportunities for intervention.

SUMMARY

Recent prospective studies have confirmed a high, if not universal, prevalence of persistent Giardia infections in low-and-middle income countries associated with child-growth shortfalls and altered gut permeability. However, the predominance of subclinical infections limits understanding of the true clinical impact of endemic pediatric giardiasis, and global disease burdens remain uncalculated. Integrating the role of Giardia in multipathogen enteropathies and how nutritional, microbial, metabolic, and pathogen-strain variables influence Giardia infection outcomes could sharpen delineations between pathogenic and potentially beneficial attributes of this enigmatic parasite.

Intestinal immune responses to commensal and pathogenic protozoa

The physical barrier of the intestine and associated mucosal immunity maintains a delicate homeostatic balance between the host and the external environment by regulating immune responses to commensals, as well as functioning as the first line of defense against pathogenic microorganisms. Understanding the orchestration and characteristics of the intestinal mucosal immune response during commensal or pathological conditions may provide novel insights into the mechanisms underlying microbe-induced immunological tolerance, protection, and/or pathogenesis. Over the last decade, our knowledge about the interface between the host intestinal mucosa and the gut microbiome has been dominated by studies focused on bacterial communities, helminth parasites, and intestinal viruses. In contrast, specifically how commensal and pathogenic protozoa regulate intestinal immunity is less well studied. In this review, we provide an overview of mucosal immune responses induced by intestinal protozoa, with a major focus on the role of different cell types and immune mediators triggered by commensal (Blastocystis spp. and Tritrichomonas spp.) and pathogenic (Toxoplasma gondii, Giardia intestinalis, Cryptosporidium parvum) protozoa. We will discuss how these various protozoa modulate innate and adaptive immune responses induced in experimental models of infection that benefit or harm the host.

Codelivery of Antigens and Adjuvant in Polymeric Nanoparticles Coated With Native Parasite Membranes Induces Protective Mucosal Immunity Against Giardia lamblia

The protozoan pathogen Giardia lamblia is an important worldwide cause of diarrheal disease and malabsorption. Infection is managed with antimicrobials, although drug resistance and treatment failures are a clinical challenge. Prior infection provides significant protection, yet a human vaccine has not been realized. Individual antigens can elicit partial protection in experimental models, but protection is weaker than after prior infection. Here, we developed a multivalent nanovaccine by coating membranes derived from the parasite onto uniform and stable polymeric nanoparticles loaded with a mucosal adjuvant. Intranasal immunization with the nanovaccine induced adaptive immunity and effectively protected mice from G. lamblia infection.

Infant Nutrition in Low- and Middle-Income Countries

The burden of infant malnutrition is greatest in low- and middle-income countries (LMICs). Infant malnutrition is defined based on distinct subcategories, among them stunting (low-height-for-age) and wasting (low-weight-for-height). Some experts are shifting more toward understanding the interplay between these overlapping phenotypes and other confounding factors such as maternal nutrition and environmental hygiene. Current guidelines emphasize appropriate breastfeeding and nutrition within the 1000 days from conception to a child's second birthday to optimize early development. Future research directed toward better biomarkers of malnutrition before acute clinical symptoms develop will help direct targeted efforts toward at-risk populations.

Giardia intestinalis thymidine kinase is a high-affinity enzyme crucial for DNA synthesis and an exploitable target for drug discovery

Giardiasis is a diarrheal disease caused by the unicellular parasite Giardia intestinalis, for which metronidazole is the main treatment option. The parasite is dependent on exogenous deoxyribonucleosides for DNA replication and thus is also potentially vulnerable to deoxyribonucleoside analogs. Here, we characterized the G. intestinalis thymidine kinase, a divergent member of the thymidine kinase 1 family that consists of two weakly homologous parts within one polypeptide. We found that the recombinantly expressed enzyme is monomeric, with 100-fold higher catalytic efficiency for thymidine compared to its second-best substrate, deoxyuridine, and is furthermore subject to feedback inhibition by dTTP. This efficient substrate discrimination is in line with the lack of thymidylate synthase and dUTPase in the parasite, which makes deoxy-UMP a dead-end product that is potentially harmful if converted to deoxy-UTP. We also found that the antiretroviral drug azidothymidine (AZT) was an equally good substrate as thymidine and was active against WT as well as metronidazole-resistant G. intestinalis trophozoites. This drug inhibited DNA synthesis in the parasite and efficiently decreased cyst production in vitro, which suggests that it could reduce infectivity. AZT also showed a good effect in G. intestinalis–infected gerbils, reducing both the number of trophozoites in the small intestine and the number of viable cysts in the stool. Taken together, these results suggest that the absolute dependency of the parasite on thymidine kinase for its DNA synthesis can be exploited by AZT, which has promise as a future medication effective against metronidazole-refractory giardiasis.

Mucosal Defense Against Giardia at the Intestinal Epithelial Cell Interface

Human giardiasis, caused by the protozoan parasite Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis, Lamblia intestinalis), is one of the most commonly-identified parasitic diseases worldwide. Chronic G. duodenalis infections cause a malabsorption syndrome that may lead to failure to thrive and/or stunted growth, especially in children in developing countries. Understanding the parasite/epithelial cell crosstalk at the mucosal surfaces of the small intestine during human giardiasis may provide novel insights into the mechanisms underlying the parasite-induced immunopathology and epithelial tissue damage, leading to malnutrition. Efforts to identify new targets for intervening in the development of intestinal immunopathology and the progression to malnutrition are critical. Translating these findings into a clinical setting will require analysis of these pathways in cells and tissues from humans and clinical trials could be devised to determine whether interfering with unwanted mucosal immune responses developed during human giardiasis provide better therapeutic benefits and clinical outcomes for G. duodenalis infections in humans.

Genotypic and Epidemiologic Profiles of Giardia duodenalis in Four Brazilian Biogeographic Regions

Human infections with gut protozoan parasites are neglected and not targeted by specific control initiatives, leading to a knowledge gap concerning their regional diversity and epidemiology. The present study aims to explore Giardia duodenalis genetic diversity and assess the epidemiologic scenario of subclinical infections in different Brazilian biogeographic regions. Cross-sectional surveys (n = 1334 subjects) were conducted in four municipalities in order to obtain fecal samples and socioenvironmental data. Microscopy of non-diarrheal feces and nucleotide sequencing of a β-giardin gene fragment were performed. From a total of 51 samples that could be sequenced, 27 (52.9%) β-giardin sequences were characterized as assemblage A and 24 (47.1%) as assemblage B. In the Amazon, assemblage B was the most frequently detected, predominantly BIII, and with two novel sub-assemblages. Assemblage A predominated in the extra-Amazon region, with five novel sub-assemblages. Prevalence reached 17.8% (64/360) in the Amazon, 8.8% (48/544) in the Atlantic Forest, 7.4% (22/299) in Cerrado and 2.3% (3/131) in the Semiarid. People living in poverty and extreme poverty presented significantly higher positivity rates. In conclusion, subclinical giardiasis is endemic in Brazilian communities in different biogeographic regions, presenting high genetic diversity and a heterogeneous genotypic distribution.

Different Drugs, Same End: Ultrastructural Hallmarks of Autophagy in Pathogenic Protozoa

Protozoan parasites interact with a wide variety of organisms ranging from bacteria to humans, representing one of the most common causes of parasitic diseases and an important public health problem affecting hundreds of millions of people worldwide. The current treatment for these parasitic diseases remains unsatisfactory and, in some cases, very limited. Treatment limitations together with the increased resistance of the pathogens represent a challenge for the improvement of the patient’s quality of life. The continuous search for alternative preclinical drugs is mandatory, but the mechanisms of action of several of these compounds have not been described. Electron microscopy is a powerful tool for the identification of drug targets in almost all cellular models. Interestingly, ultrastructural analysis showed that several classes of antiparasitic compounds induced similar autophagic phenotypes in trypanosomatids, trichomonadids, and apicomplexan parasites as well as in Giardia intestinalis and Entamoeba spp. with the presence of an increased number of autophagosomes as well as remarkable endoplasmic reticulum profiles surrounding different organelles. Autophagy is a physiological process of eukaryotes that maintains homeostasis by the self-digestion of nonfunctional organelles and/or macromolecules, limiting redundant and damaged cellular components. Here, we focus on protozoan autophagy to subvert drug effects, discussing its importance for successful chemotherapy.

Full breastfeeding protection against common enteric bacteria and viruses: results from the MAL-ED cohort study

BACKGROUND

Breastfeeding is known to reduce the risk of enteropathogen infections, but protection from specific enteropathogens is not well characterized.

OBJECTIVE

The aim was to estimate the association between full breastfeeding (days fed breast milk exclusively or with nonnutritive liquids) and enteropathogen detection.

METHODS

A total of 2145 newborns were enrolled at 8 sites, of whom 1712 had breastfeeding and key enteropathogen data through 6 mo. We focused on 11 enteropathogens: adenovirus 40/41, norovirus, sapovirus, astrovirus, and rotavirus, enterotoxigenic Escherichia coli (ETEC), Campylobacter spp., and typical enteropathogenic E. coli as well as entero-aggregative E. coli, Shigella and Cryptosporidium. Logistic regression was used to estimate the risk of enteropathogen detection in stools and survival analysis was used to estimate the timing of first detection of an enteropathogen.

RESULTS

Infants with 10% more days of full breastfeeding within the preceding 30 d of a stool sample were less likely to have the 3 E. coli and Campylobacter spp. detected in their stool (mean odds: 0.92-0.99) but equally likely (0.99-1.02) to have the viral pathogens detected in their stool. A 10% longer period of full breastfeeding from birth was associated with later first detection of the 3 E. coli, Campylobacter, adenovirus, astrovirus, and rotavirus (mean HRs of 0.52-0.75). The hazards declined and point estimates were not statistically significant at 3 mo.

CONCLUSIONS

In this large multicenter cohort study, full breastfeeding was associated with lower likelihood of detecting 4 important enteric pathogens in the first 6 mo of life. These results also show that full breastfeeding is related to delays in the first detection of some bacterial and viral pathogens in the stool. As several of these pathogens are risk factors for poor growth during childhood, this work underscores the importance of exclusive or full breastfeeding during the first 6 mo of life to optimize early health.

A review of the molecular epidemiology of Cryptosporidium spp. and Giardia duodenalis in the Middle East and North Africa (MENA) region

Cryptosporidium spp. and Giardia duodenalis are important protozoan parasites which are associated with diarrheal diseases in humans and animals worldwide. Relatively little is known about the molecular epidemiology of Cryptosporidium spp. and Giardia duodenalis in the Middle East Countries and North Africa (MENA region). Therefore, this review aimed to inspect published genotyping and subtyping studies on Cryptosporidium spp. and Giardia duodenalis in the MENA region. These studies indicate that both anthroponotic and zoonotic transmission of Cryptosporidium occurs with the predominance of zoonotic transmission in most countries. Seven Cryptosporidium species were identified in humans (C. parvum, C. hominis, Cryptosporidium meleagridis, C. felis, Cryptosporidium muris, C. canis and C. bovis), with C. parvum by far being the most prevalent species (reported in 95.4% of the retrieved studies). Among C. parvum gp60 subtype families, IIa and IId predominated, suggesting potential zoonotic transmission. However, in four MENA countries (Lebanon, Israel, Egypt and Tunisia), C. hominis was the predominant species with five subtype families reported including Ia, Ib, Id, If and Ie, all of which are usually anthroponotically transmitted between humans. In animals, the majority of studies were conducted mainly on livestock and poultry, 15 species were identified (C. parvum, C. hominis, C. muris, Cryptosporidium cuniculus, C. andersoni, C. bovis, C. meleagridis, C. baileyi, C. erinacei, C. ryanae, C. felis, C. suis, Cryptosporidium galli, C. xiaoi and C. ubiquitum) with C. parvum (IIa and IId subtypes) the dominant species in livestock and C. meleagridis and C. baileyi the dominant species in poultry. With G. duodenalis, five assemblages (A, B, C, E and F) were identified in humans and six (A, B, C, E, D and F) in animals in MENA countries with assemblages A and B commonly reported in humans, and assemblages A and E dominant in livestock. This review also identified a major knowledge gap in the lack of Cryptosporidium spp. and Giardia duodenalis typing studies in water and food sources in the MENA region. Of the few studies conducted on water sources (including drinking and tap water), ten Cryptosporidium species and four genotypes were identified, highlighting the potential role of water as the major route of Cryptosporidium spp. transmission in the region. In addition, three G. duodenalis assemblages (A, B and E) were detected in different water sources with AI, AII and BIV being the main sub-assemblages reported. More research is required in order to better understand the molecular diversity and transmission dynamics of Cryptsporidum spp. and Giardia duodenalis in humans, animals, water and food sources in MENA region.

Intestinal permeability before and after albendazole treatment in low and high socioeconomic status schoolchildren in Makassar, Indonesia

Intestinal helminths are highly prevalent in low-SES children and could contribute to poor health outcomes either directly or via alteration of the gut microbiome and gut barrier function. We analysed parasitic infections and gut microbiota composition in 325 children attending high- and low-SES schools in Makassar, Indonesia before and after albendazole treatment. Lactulose/Mannitol Ratio (LMR, a marker of gut permeability); I-FABP (a surrogate marker of intestinal damage) as well as inflammatory markers (LBP) were measured. Helminth infections were highly prevalent (65.6%) in low-SES children. LMR and I-FABP levels were higher in low-SES children (geomean (95%CI): 4.03 (3.67-4.42) vs. 3.22 (2.91-3.57); p. adj < 0.001; and 1.57 (1.42-1.74) vs. 1.25 (1.13-1.38); p. adj = 0.02, respectively) while LBP levels were lower compared to the high-SES (19.39 (17.09-22.01) vs. 22.74 (20.07-26.12); p.adj = 0.01). Albendazole reduced helminth infections in low-SES and also decreased LMR with 11% reduction but only in helminth-uninfected children (estimated treatment effect: 0.89; p.adj = 0.01). Following treatment, I-FABP decreased in high- (0.91, p.adj < 0.001) but increased (1.12, p.adj = 0.004) in low-SES children. Albendazole did not alter the levels of LBP. Microbiota analysis showed no contribution from specific bacterial-taxa to the changes observed. Intestinal permeability and epithelial damage are higher while peripheral blood inflammatory marker is lower in children of low-SES in Indonesia. Furthermore, treatment decreased LMR in helminth-uninfected only.

A scoping review of risk factors and transmission routes associated with human giardiasis outbreaks in high-income settings

The flagellated pathogen Giardia duodenalis is one of the leading causes of parasitic gastrointestinal illness worldwide. In many higher income countries, such as the United Kingdom, the disease is often perceived as being travel-related, likely leading to the under-reporting of sporadic cases and outbreaks. A summary of the literature describing outbreaks and risk factors in higher income countries is necessary to improve our understanding of this pathogen and identify existing knowledge gaps. Initial literature searches were carried out in September 2016 and updated at regular intervals until November 2021, using appropriate search terms in Medline, Embase and PubMed databases. A total of 75 papers met the inclusion criteria, revealing that the consumption of contaminated water and contact with young children of diaper-wearing age were the most common transmission routes leading to outbreaks of giardiasis. Of the ten studies where food was primarily associated with outbreaks, food handlers accounted for eight of these. Another reported transmission route was direct contact with fecal material, which was reported in six studies as the primary transmission route. Travel-associated giardiasis was considered the sole transmission route in two studies, whereas multiple transmission routes contributed to giardiasis outbreaks in eleven studies. The evidence around zoonotic transmission was less clear and hampered by the lack of robust and regularly applied parasite molecular typing techniques. This literature review summarizes the findings of Giardia outbreak investigations and epidemiological studies in high-income countries. Transmission routes are identified and discussed to highlight the associated risk factors. These data also indicate gaps in our current knowledge that include the need for robust, in-depth molecular studies and have underscored the importance of water as a transmission route for Giardia cysts. These future molecular studies will improve our understanding of Giardia epidemiology and transmission pathways in higher income countries to prevent spread of this significantly under-reported pathogen.

MicroRNA Expression and Intestinal Permeability in Children Living in a Slum Area of Bangladesh

Introduction: MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression. Changes in miRNA expression have been reported in a number of intestinal diseases, in both tissue samples and readily accessible specimens like stools. Pathogenic infections, diet, toxins, and other environmental factors are believed to influence miRNA expression. However, modulation of miRNAs in humans is yet to be thoroughly investigated. In this study, we examined the expression levels of two human miRNAs (miRNA-122 and miRNA-21) in stool samples of a group of Bangladeshi children who had an altered/increased intestinal permeability (IIP). Methods: Stool samples were collected from children with IIP (L:M > 0.09) and normal intestinal permeability (NIP) (L:M ≤ 0.09). Quantitative PCR was performed to quantify the levels of miRNA-122 and miR-21 in stools. Commercial ELISA kits were used to measure gut inflammatory markers Calprotectin and REG1B. Serum samples were tested using Human Bio-Plex Pro Assays to quantify IL-1β, IL-2, IL-5, IL-10, IL-13, IFN-γ, and TNF-α. Total nucleic acid extracted from stool specimens were used to determine gut pathogens using TaqMan Array Card (TAC) system real-time polymerase chain reaction. Results: The expression levels of miRNA-122 (fold change 11.6; p < 0.001, 95% CI: 6.14-11.01) and miR-21 (fold change 10; p < 0.001, 95% CI: 5.05-10.78) in stool were upregulated in children with IIP than in children with normal intestinal permeability (NIP). Significant correlations were observed between stool levels of miR-122 and miR-21 and the inflammatory cytokines IL-1β, IL-2, IFN-γ, and TNF-α (p < 0.05). Children with IIP were frequently infected with rotavirus, Campylobacter jejuni, Bacteroides fragilis, adenovirus, norovirus, astrovirus, and various Escherichia coli strains (ETEC_STh, ETEC_STp, EAEC_aaiC, EAEC_aatA) (p < 0.001). miR-122 significantly correlated with the fecal inflammatory biomarkers REG1B (p = 0.015) and Calprotectin (p = 0.030), however miR-21 did not show any correlation with these fecal biomarkers.

Benefits and Risks of Smallholder Livestock Production on Child Nutrition in Low- and Middle-Income Countries

Livestock production may improve nutritional outcomes of pregnant women and children by increasing household income, availability of nutrient-dense foods, and women's empowerment. Nevertheless, the relationship is complex, and the nutritional status of children may be impaired by presence of or proximity to livestock and their pathogens. In this paper, we review the benefits and risks of livestock production on child nutrition. Evidence supports the nutritional benefits of livestock farming through income, production, and women's empowerment. Increasing animal source food consumption requires a combination of efforts, including improved animal management so that herd size is adequate to meet household income needs and consumption and addressing sociocultural and gendered norms. Evidence supports the inclusion of behavior change communication strategies into livestock production interventions to facilitate the sustainability of nutritional benefits over time, particularly interventions that engage women and foster dimensions of women's empowerment. In evaluating the risks of livestock production, evidence indicates that a broad range of enteric pathogens may chronically infect the intestines of children and, in combination with dietary deficits, may cause environmental enteric dysfunction (EED), a chronic inflammation of the gut. Some of the most important pathogens associated with EED are zoonotic in nature with livestock as their main reservoir. Very few studies have aimed to understand which livestock species contribute most to colonization with these pathogens, or how to reduce transmission. Control at the point of exposure has been investigated in a few studies, but much less effort has been spent on improving animal husbandry practices, which may have additional benefits. There is an urgent need for dedicated and long-term research to understand which livestock species contribute most to exposure of young children to zoonotic enteric pathogens, to test the potential of a wide range of intervention methods, to assess their effectiveness in randomized trials, and to assure their broad adaptation and sustainability. This review highlights the benefits and risks of livestock production on child nutrition. In addition to identifying research gaps, findings support inclusion of poor gut health as an immediate determinant of child undernutrition, expanding the established UNICEF framework which includes only inadequate diet and disease.

Giardia duodenalis: Biology and Pathogenesis

Giardia duodenalis captured the attention of Leeuwenhoek in 1681 while he was examining his own diarrheal stool, but, ironically, it did not really gain attention as a human pathogen until the 1960s, when outbreaks were reported. Key technological advances, including in vitro cultivation, genomic and proteomic databases, and advances in microscopic and molecular approaches, have led to an understanding that this is a eukaryotic organism with a reduced genome rather than a truly premitochondriate eukaryote. This has included the discovery of mitosomes (vestiges of mitochondria), a transport system with many of the features of the Golgi apparatus, and even evidence for a sexual or parasexual cycle. Cell biology approaches have led to a better understanding of how Giardia survives with two nuclei and how it goes through its life cycle as a noninvasive organism in the hostile environment of the lumen of the host intestine. Studies of its immunology and pathogenesis have moved past the general understanding of the importance of the antibody response in controlling infection to determining the key role of the Th17 response. This work has led to understanding of the requirement for a balanced host immune response that avoids the extremes of an excessive response with collateral damage or one that is unable to clear the organism. This understanding is especially important in view of the remarkable ranges of early manifestations, which range from asymptomatic to persistent diarrhea and weight loss, and longer-term sequelae that include growth stunting in children who had no obvious symptoms and a high frequency of postinfectious irritable bowel syndrome (IBS).

Diarrheal Pathogens Associated With Growth and Neurodevelopment

Background

Diarrheal pathogens have been associated with linear growth deficits. The effect of diarrheal pathogens on growth is likely due to inflammation, which also adversely affects neurodevelopment. We hypothesized that diarrheagenic pathogens would be negatively associated with both growth and neurodevelopment.

Methods

We conducted a longitudinal birth cohort study of 250 children with diarrheal surveillance and measured pathogen burden in diarrheal samples using quantitative polymerase chain reaction. Pathogen attributable fraction estimates of diarrhea over the first 2 years of life, corrected for socioeconomic variables, were used to predict both growth and scores on the Bayley-III Scales of Infant and Toddler Development.

Results

One hundred eighty children were analyzed for growth and 162 for neurodevelopmental outcomes. Rotavirus, Campylobacter, and Shigella were the leading causes of diarrhea in year 1 while Shigella, Campylobacter, and heat-stable toxin–producing enterotoxigenic Escherichia coli were the leading causes in year 2. Norovirus was the only pathogen associated with length-for-age z score at 24 months and was positively associated (regression coefficient [RC], 0.42 [95% confidence interval {CI}, .04 to .80]). Norovirus (RC, 2.46 [95% CI, .05 to 4.87]) was also positively associated with cognitive scores while sapovirus (RC, –2.64 [95% CI, –4.80 to –.48]) and typical enteropathogenic E. coli (RC, –4.14 [95% CI, –8.02 to –.27]) were inversely associated. No pathogens were associated with language or motor scores. Significant maternal, socioeconomic, and perinatal predictors were identified for both growth and neurodevelopment.

Conclusions

Maternal, prenatal, and socioeconomic factors were common predictors of growth and neurodevelopment. Only a limited number of diarrheal pathogens were associated with these outcomes.

Gut integrity and duodenal enteropathogen burden in undernourished children with environmental enteric dysfunction

Environmental enteric dysfunction (EED) is a subclinical condition of intestinal inflammation, barrier dysfunction and malabsorption associated with growth faltering in children living in poverty. This study explores association of altered duodenal permeability (lactulose, rhamnose and their ratio) with higher burden of enteropathogen in the duodenal aspirate, altered histopathological findings and higher morbidity (diarrhea) that is collectively associated with linear growth faltering in children living in EED endemic setting. In a longitudinal birth cohort, 51 controls (WHZ > 0, HAZ > −1.0) and 63 cases (WHZ< -2.0, refractory to nutritional intervention) were recruited. Anthropometry and morbidity were recorded on monthly bases up to 24 months of age. Dual sugar assay of urine collected after oral administration of lactulose and rhamnose was assessed in 96 children from both the groups. Duodenal histopathology (n = 63) and enteropathogen analysis of aspirate via Taqman array card (n = 60) was assessed in only cases. Giardia was the most frequent pathogen and was associated with raised L:R ratio (p = 0.068). Gastric microscopy was more sensitive than duodenal aspirate in H. pylori detection. Microscopically confirmed H. pylori negatively correlated with HAZ at 24 months (r = −0.313, p = 0.013). Regarding histopathological parameters, goblet cell reduction significantly correlated with decline in dual sugar excretion (p< 0.05). Between cases and controls, there were no significant differences in the median (25^th, 75^th percentile) of urinary concentrations (μg/ml) of lactulose [27.0 (11.50, 59.50) for cases vs. 38.0 (12.0, 61.0) for controls], rhamnose [66.0 (28.0, 178.0) vs. 86.5 (29.5, 190.5)] and L:R ratio [0.47 (0.24, 0.90) vs. 0.51 (0.31, 0.71)] respectively. In multivariable regression model, 31% of variability in HAZ at 24 months of age among cases and controls was explained by final model including dual sugars. In conclusion, enteropathogen burden is associated with altered histopathological features and intestinal permeability. In cases and controls living in settings of endemic enteropathy, intestinal permeability test may predict linear growth. However, for adoption as a screening tool for EED, further validation is required due to its complex intestinal pathophysiology.

EED is a subclinical condition of compromised gut integrity secondary to frequent and repeated exposure to enteropathogens in global settings with a high prevalence of undernutrition. In this study, we reported association of gut mucosal architecture with a dual sugar intestinal permeability assay (lactulose-rhamnose) in Pakistani children. In the presence of duodenal enteropathogens, features such as chronic inflammation, intra-epithelial lymphocytosis, enterocyte injury and Paneth cell reduction were consistently observed. When comparing undernourished cases and controls living in the same setting, we found urinary excretion of the sugars was similar among groups; however, variability in HAZ among children at 24 months was partially explained by a model that includes excretion values.

Disturbed gut microbiota and bile homeostasis in Giardia-infected mice contributes to metabolic dysregulation and growth impairment

Although infection with the human enteropathogen Giardia lamblia causes self-limited diarrhea in adults, infant populations in endemic areas experience persistent pathogen carriage in the absence of diarrhea. The persistence of this protozoan parasite in infants has been associated with reduced weight gain and linear growth (height-for-age). The mechanisms that support persistent infection and determine the different disease outcomes in the infant host are incompletely understood. Using a neonatal mouse model of persistent G. lamblia infection, we demonstrate that G. lamblia induced bile secretion and used the bile constituent phosphatidylcholine as a substrate for parasite growth. In addition, we show that G. lamblia infection altered the enteric microbiota composition, leading to enhanced bile acid deconjugation and increased expression of fibroblast growth factor 15. This resulted in elevated energy expenditure and dysregulated lipid metabolism with reduced adipose tissue, body weight gain, and growth in the infected mice. Our results indicate that this enteropathogen's modulation of bile acid metabolism and lipid metabolism in the neonatal mouse host led to an altered body composition, suggesting how G. lamblia infection could contribute to growth restriction in infants in endemic areas.

Giardiasis treatment: an update with a focus on refractory disease

PURPOSE OF REVIEW

Giardiasis remains a common cause of diarrhea and intestinal enteropathy globally. Here we give an overview of clinical treatment studies and discuss potential mechanisms and molecular targets for in-vitro testing of drug resistance.

RECENT FINDINGS

Giardia is a cause of disease both in diarrheal and nondiarrheal cases. The prevalence of treatment refractory giardiasis is increasing. Recent studies reveal 5-nitroimidazole refractory infection occurs in up to 50% of cases. Mechanisms of drug resistance are not known. Placebo controlled studies of drug efficacy, taking the self-limiting course of giardiasis into account, has not been reported. No randomized controlled trials of treatment of refractory infection have been performed the last 25 years. Based on the clinical studies reported, combination treatment with a 5-nitroimidazole and a benzimidazole is more effective than repeated courses of 5-nitroimidazole or monotherapies in refractory cases. Quinacrine is effective in refractory cases, but potentially severe side effects limit its use.

SUMMARY

A combination of a 5-nitroimidazole and albendazole or mebendazole, and quinacrine monotherapy, are rational choices in nitroimidazole refractory infections, but randomized controlled studies are needed. Further research into more recent clinical isolates is necessary to uncover mechanisms for the increase in metronidazole refractory giardiasis observed during the last decade.

Modeling Enteropathy or Diarrhea with the Top Bacterial and Protozoal Pathogens: Differential Determinants of Outcomes

Developing effective therapeutics or preventive interventions for important health threats is greatly enhanced whenever accessible models can enable the assessment of clinically important outcomes. While no non-human model is ever perfect, inexpensive in vivo small animal models in such as mice are often of great help in assessing the relevant efficacy of potential interventions. In addition to acute diarrhea, the long-term growth and developmental effects of enteric infections, with or without overt diarrhea, are increasingly recognized. To address these diverse effects, inexpensive animal models are proving to be very helpful. Herein, we review the major clinical concerns with enteric parasitic and bacterial infections that are extremely common worldwide, especially in vulnerable young children living in impoverished areas, and the recently published murine models of these infections and their outcomes. We find that common dietary deficiencies seen in children in developing areas have striking effects on diarrhea and enteropathy outcomes in mice. However, these effects differ with different pathogens. Specifically, the effects of protein or zinc deficiency differ considerably with different major protozoal and bacterial pathogens, suggesting different pathogenetic pathways and intervention effects. The pathogens reviewed are the seven top parasitic and bacterial pathogens seen in children, namely, Cryptosporidium, Giardia, Campylobacter, Shigella, enterotoxigenic Escherichia coli (ETEC), enteroaggregative E. coli (EAEC), and enteropathogenic E. coli (EPEC).

Effects of an urban sanitation intervention on childhood enteric infection and diarrhea in Maputo, Mozambique: A controlled before-and-after trial

We conducted a controlled before-and-after trial to evaluate the impact of an onsite urban sanitation intervention on the prevalence of enteric infection, soil transmitted helminth re-infection, and diarrhea among children in Maputo, Mozambique. A non-governmental organization replaced existing poor-quality latrines with pour-flush toilets with septic tanks serving household clusters. We enrolled children aged 1-48 months at baseline and measured outcomes before and 12 and 24 months after the intervention, with concurrent measurement among children in a comparable control arm. Despite nearly exclusive use, we found no evidence that intervention affected the prevalence of any measured outcome after 12 or 24 months of exposure. Among children born into study sites after intervention, we observed a reduced prevalence of Trichuris and Shigella infection relative to the same age group at baseline (<2 years old). Protection from birth may be important to reduce exposure to and infection with enteric pathogens in this setting.

Protection From Natural Immunity Against Enteric Infections and Etiology-Specific Diarrhea in a Longitudinal Birth Cohort

BACKGROUND

The degree of protection conferred by natural immunity is unknown for many enteropathogens, but it is important to support the development of enteric vaccines.

METHODS

We used the Andersen-Gill extension of the Cox model to estimate the effects of previous infections on the incidence of subsequent subclinical infections and diarrhea in children under 2 using quantitative molecular diagnostics in the MAL-ED cohort. We used cross-pathogen negative control associations to correct bias due to confounding by unmeasured heterogeneity of exposure and susceptibility.

RESULTS

Prior rotavirus infection was associated with a 50% lower hazard (calibrated hazard ratio [cHR], 0.50; 95% confidence interval [CI], 0.41-0.62) of subsequent rotavirus diarrhea. Strong protection was evident against Cryptosporidium diarrhea (cHR, 0.32; 95% CI, 0.20-0.51). There was also protection due to prior infections for norovirus GII (cHR against diarrhea, 0.67; 95% CI, 0.49-0.91), astrovirus (cHR, 0.62; 95% CI, 0.48-0.81), and Shigella (cHR, 0.79; 95% CI, 0.65-0.95). Minimal protection was observed for other bacteria, adenovirus 40/41, and sapovirus.

CONCLUSIONS

Natural immunity was generally stronger for the enteric viruses than bacteria, potentially due to less antigenic diversity. Vaccines against major causes of diarrhea may be feasible but likely need to be more immunogenic than natural infection.

Impact of Annual Albendazole versus Four-Monthly Test-and-Treat Approach of Intestinal Parasites on Children Growth-A Longitudinal Four-Arm Randomized Parallel Trial during Two Years of a Community Follow-Up in Bengo, Angola

Malnutrition and intestinal parasites continue to have serious impacts on growth and cognitive development of children in Angola. A longitudinal four-arm randomized parallel trial was conducted to investigate if deworming with a single annual dose of albendazole (annual-ALB) or a four-monthly test-and-treat (4TT) intestinal parasites approach at individual or household levels improve nutritional outcomes of pre-school children in Bengo province. Children with intestinal parasites (n = 121) were randomly assigned (1:1:1:1) to arm A1: annual-ALB*individual level; A2: annual-ALB*household level; A3: 4TT*individual; and A4: 4TT*household level. At baseline, 4, 8, 12, 16, 20, and 24 months of follow-up, growth was assessed by height, weight, height-for-age, weight-for-height, weight-for-age, and mid-upper arm circumference. Intention-to-treat analysis was done using non-parametric approach, mixed effect models, and generalized estimating equations (GEE). Initially, 57% and 26% of the children were infected by Giardia lamblia and Ascaris lumbricoides, respectively. This study did not show that a 4TT intestinal parasites approach results on better growth outcomes of children (height, weight, HAZ, WAZ, WHZ and MUACZ) when compared with annual ALB, with exception of height and WHZ using GEE model at 5% level. Positive temporal effects on most nutrition outcomes were observed. Implementing a longitudinal study in a poor setting is challenging and larger sample sizes and 'pure and clean' data are difficult to obtain. Nevertheless, learned lessons from this intensive study may contribute to future scientific research and to tailor multidisciplinary approaches to minimize malnutrition and infections in resource-poor countries.

Molecular Epidemiology of Giardia Infections in the Genomic Era

Giardia duodenalis is a major gastrointestinal parasite of humans and animals across the globe. It is also of interest from an evolutionary perspective as it possesses many features that are unique among the eukaryotes, including its distinctive binucleate cell structure. While genomic analysis of a small number of isolates has provided valuable insights, efforts to understand the epidemiology of the disease and the population biology of the parasite have been limited by the molecular tools currently available. We review these tools and assess the impact of affordable and rapid genome sequencing systems increasingly being deployed in diagnostic settings. While these technologies have direct implications for public and veterinary health, they will also improve our understanding of the unique biology of this fascinating parasite.

Multilocus genotyping of Giardia duodenalis in Bactrian camels (Camelus bactrianus) in China

The protozoan parasite Giardia duodenalis is known to infect humans and a wide range of animals globally. However, no studies on G. duodenalis infection in Bactrian camels have been reported. In the present study, in order to examine the prevalence and genetic diversity of G. duodenalis in Bactrian camels, 852 fecal samples were collected from 24 sampling sites in three geographical areas (Gansu province, Inner Mongolia, and Xinjiang Uygur autonomous regions) of northwestern China, and subjected to multilocus sequence typing (MLST) analysis targeting the 18S rRNA, β-giardin (bg), glutamate dehydrogenase (gdh), and triosephosphate isomerase (tpi) genes. About 84 fecal samples tested positive for Giardia infection, with an overall prevalence of 9.8%, including three samples from camel calves with diarrhea. Significant differences (χ² = 80.7, df = 2, P < 0.01) in the prevalence were found in Bactrian camels belonging to three geographical areas, with the highest (33.3%) in Gansu province and the lowest (4.2%) in Xinjiang Uygur autonomous region. Furthermore, significantly different prevalences (χ² = 34.2, df = 2, P < 0.01) were revealed among age groups, with the highest (35.7%) in camels aged 3 to 6 years old, and the lowest (7.5%) in camels aged > 6 years old. Sequence analysis identified two assemblages, including zoonotic assemblage A and ungulate-adapted assemblage E, with the latter as the dominant G. duodenalis assemblage in each age group and at all sampling sites having positive samples except Hotan. Genetic variations were detected among G. duodenalis isolates in these camels, and eight, three, and seven haplotypes were identified at loci bg, gdh, and tpi, respectively, forming two multilocus genotypes (MLGs) of zoonotic assemblage A and one MLG of assemblage E. To the best of our knowledge, this is the first report on G. duodenalis infection in Bactrian camels, and the data indicate that G. duodenalis have a broad host range.